Russia's cooperation with Europe in the Iranian nuclear standoff could be curbed if unilateral EU sanctions on Tehran hit Russian companies, a top envoy said Friday.

Russia's ambassador to the European Union, Vladimir Chizhov, slammed decisions last week by the EU and United States to impose sanctions on Iran's oil and gas sector that go beyond new UN measures backed by Moscow.

"We do not support them. We think they are totally wrong in substance and in tactics," Chizhov told reporters in Brussels.

"The sanctions contained in (UN Security Council) Resolution 1929 are clever sanctions, the follow-on measures by the European Union are not," he said.

"If you want to dissuade Iran from pursuing a nuclear programme ... then why the hell are you banning the supply of equipment for the oil and gas industry?"

EU sanctions approved at a June 17 summit include a ban on new investment, technical assistance and technology transfers to Iran's huge gas and oil industry, particularly for refining and liquefied natural gas.

The US Congress approved Thursday a bill to shut US markets to firms that provide Iran with the refined petroleum products it needs to meet demand because of a weak domestic refining capability.

Russian President Dmitry Medvedev also criticised the US and EU sanctions last week, and Iran's deputy oil minister Ali Reza Zeighami on Friday said they would only serve to make Iran petrol self-sufficient within two years.

"The more Americans and Europeans sanction us, the closer it takes us to self-sufficiency," Fars news agency quoted Zeighami, who also heads the National Iranian Oil Refining and Distribution Company, as saying.

"Despite sanctions, in two years' time we will be self-sufficient in providing petrol, and two years after that we will be able to be a petrol exporter," Zeighami said.

Russia's Chizhov said the unilateral sanctions will "certainly hinder" diplomatic efforts to convince Iran to halt its nuclear activities because Iranian officials "will immediately sense a difference of views" among world powers.

Russia is concerned about any interference with Russian business interests in Iran, the envoy said.

"We will certainly not accept any infringement of the rights and of the activities of Russian companies on the basis of those unilateral decisions," he said.

He warned that Russian cooperation with the EU on the Iran nuclear issue could be affected by the sanctions.

"That will certainly depend on the degree to which the EU will be taking into consideration our sensitivities regarding the interests of Russian companies involved," Chizhov said.

Despite complaints from the West, Russia is helping build Iran's first nuclear power plant in the southern city of Bushehr. In 2008 Russian energy giant Gazprom signed an agreement with Iran to develop its oil and gas fields.

The United States, EU and Israel fear that Iran's nuclear activities are aimed at building an atomic bomb, but Tehran insists it is merely a civilian energy programme.

Russia, which unlike the United States has diplomatic ties with Iran, has in the past been reluctant to impose tough sanctions but backed the latest UN move following Tehran's repeated defiance of orders to halt uranium enrichment.

US Defence Secretary Robert Gates said last week that Russia appeared to have a "schizophrenic" approach to Iran, viewing it as a security threat while simultaneously pursuing commercial deals with the country.

"They recognise the security threat that Iran presents, but then there are these commercial opportunities, which, frankly, are not unique to them," said Gates, referring to European business ties to Iran.

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